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* Draytek Router - Security Advisory: CSRF & DNS Attacks *

Please be advised that we have become aware of a new attack affecting web connected devices, including DrayTek routers.

Check the DNS settings on your DrayTek router and install new firmware. Please read all of this advisory.


In May 2018, we became aware of new attacks against web-enabled devices, which includes DrayTek routers. The recent attacks have attempted to change DNS settings of routers.  We are in the process of releasing updated firmware, and will issue each ASAP to address this issue. You should upgrade as soon as it is available but also immediately follow the advice below:

 

  1. Update your firmware immediately, or as soon as updated software is available. Before doing the upgrade, take a backup of your current config in case you need to restore it later (system maintenance -> Config Backup).   Do use the .ALL file to upgrade, otherwise you will wipe your router settings. If you are upgrading from a much older firmware then please check the release notes carefully for any upgrading instructions.

  2. Check your DNS and DHCP settings on your router.   If you have a router supporting multiple LAN subnets, check settings for each subnet.  Your DNS settings should be either blank, set to the correct DNS server addresses from your ISP or DNS server addresses of a server which you have deliberately set (e.g. Google 8.8.8.8). A known rogue DNS server is 38.134.121.95 - if you see that, your router has been changed.  

    In the case of DHCP, the DHCP server may be disabled (in most cases of on-premise servers), which will typically cause errors on your LAN as devices fail to be issued with IP addresses so the problem is more obvious and may point the issue to your server.



  3. If your settings appear to have been compromised, restore a config backup or manually check and correct all settings. Change your admin password and check that no other admin users have been added. Follow all of the advice in our previous CSRF article here.

  4. If you have remote access enabled on your router, disable it if you don't need it, and use an access control list if possible.   If you do not have updated firmware yet, disable remote access (admin) and SSL VPN.  The ACL does not apply to SSL VPN connections (Port 443) so you should also temporarily disable SSL VPN until you have updated the firmware.



  5. Always use secured (SSL/TLS1.2) connections to your router, both LAN and WAN side. To do that, just prefix the address with https://.   Disabling non-SSL/TLS connections:



    The 'enable validation code' option at the top (above) is recommended. It adds a 'captcha' style option to the web admin login page.
     

The priority for Draytek has been to identify the cause and issue strengthened firmware so this is an initial report/advisory. They will continue to monitor and investigate this issue and will update as appropriate.  At this stage, for obvious security reasons,  Draytek will not be providing any further details of the issue. Please share this advisory with other DrayTek users.

Our wireless access points (VigorAP series), switches (VigorSwitch series) and Vigor 2950, 2955, 2960, 3900 and 3300 series routers are not affected and do not need updating (but you should still always run the latest firmware on those anyway).   

 

Why would someone want to change my DNS?

 

Changing your DNS server address might seem like a strange and very minor setting for a hacker to change but it is likely to be 'phase 1' of a larger attack.  A DNS server converts web addresses (like www.somewebsite.com) into an IP address (194.114.12.12 or 2001:db8::1) - the Internet router IP uses numeric addresses, not names. 

 

If someone can redirect you to a rogue DNS server, they can misdirect your browser to a fake site when you think you're going to your favourite web site. You login but now the criminals have your username and password (another reason people should use 2FA). The site will normally redirect you back to the genuine web site to avoid arousing suspicion.  This could be a banking site, social media, other financial site or anything else. If your DNS has been changed, we recommend changing passwords of any sites you have accessed recently, particularly financial ones, as well as your router admin and wifi password(s).

 

At the time of writing, the known rogue address (38.134.121.95) is not responding to DNS queries so it may not have gone active yet, or the owner/operator of that address has now taken the compromised server offline. If your router was compromised, it will still work as the hackers set a secondary (legitimate) address of 8.8.8.8 (Google) as a fallback so that unavailability of their fake server didn't cause you to go and check your settings but don't leave it like that.


Updated Firmware Versions for UK/IE users:

 

Available for UK/IE users now:

If you have any questions  or require help with this please contact our support team here.


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  1. Scott harrington

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